GNSS Confidence Indicator via Auto-Correlation Doppler Correction
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Solution Overview
Problem
Satellite positioning systems face significant errors in determining the position of moving objects, particularly in complex terrestrial environments like urban settings, due to signal obstruction and multipath effects, leading to inaccurate trajectory calculations and potential false billing in geo-located road toll applications.
Innovation Solution
A method to determine a confidence indicator for the trajectory of a moving object using a GNSS receiver, which involves estimating successive positions, identifying trajectory segments, determining auto-correlation functions, applying Doppler delay corrections, and comparing these with theoretical functions to assess the accuracy of the trajectory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GNSS signals are received in urban environments with buildings and walls, then the receiver can still calculate position, but the geometry of satellite signals is affected and positioning accuracy deteriorates
Solution Approach 1:
The patent applies feedback by continuously monitoring the quality of GNSS signal reception through auto-correlation functions and comparing them against theoretical values. When the actual auto-correlation deviates from the theoretical expectation beyond a threshold, the system generates feedback to flag the position measurement as unreliable, enabling dynamic adjustment of billing decisions without requiring complete system failure
Solution Approach 2:
The patent substitutes direct mechanical geometric verification with a signal-processing approach using auto-correlation functions. Instead of relying solely on the geometric arrangement of satellites (which is affected by urban obstacles), the system uses signal correlation properties to detect and correct positioning errors caused by multipath effects and signal obstruction
2Ease of operation
If navigation signals are reflected off walls (multipath effect), then the receiver can still process signals, but the measured trajectory becomes inaccurate and false billing may occur
Solution Approach 1:
The system continuously compares actual auto-correlation function values against theoretical values during signal processing. When multipath reflection causes the actual correlation to deviate from theoretical expectations, the feedback mechanism detects this discrepancy and prevents incorrect trajectory-based billing, allowing continuous operation while maintaining accuracy
Solution Approach 2:
The patent converts the harmful multipath reflection effect into a detectable signal characteristic. By analyzing the auto-correlation function, the system can identify reflected signals and their distinctive correlation patterns, then use this information to either correct the position measurement or flag it as unreliable, transforming the harmful reflection into a useful detection mechanism
3Adaptability or versatility
If the receiver operates without SBAS systems in terrestrial environments, then the system is simpler and more versatile, but the ability to bound position error is significantly reduced
Solution Approach 1:
The patent enables the receiver to self-verify its own positioning accuracy by internally calculating and comparing auto-correlation functions against theoretical values. This self-service mechanism allows the system to detect and flag unreliable measurements without requiring external SBAS augmentation, maintaining versatility while improving reliability through autonomous verification
Solution Approach 2:
The system performs preliminary verification of signal quality through auto-correlation analysis before using the position data for billing purposes. By checking the correlation consistency in advance, the system prevents incorrect measurements from causing false billing, effectively preparing and validating data before it impacts the final decision
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides a confidence indicator that helps evaluate position estimation errors, ensuring accurate trajectory determination and preventing false billing by accounting for Doppler effects and signal obstructions, thereby enhancing the reliability of satellite positioning systems in challenging environments.
Implementation Method 1
the receiver effects the acquisition of radioelectric signals constituting navigation signals originating from the four satellites of the constellation
Data Source
AI summary
A method includes estimating the position of the moving object on the basis of the reception of navigation signals emitted by a constellation of satellites, the navigation signals being modulated by a code and the receiver comprising a local replica of the code. The determination of the confidence indicator consists in estimating a speed of displacement of the receiver over an identified trajectory segment, deducing therefrom a Doppler delay function corresponding to the motion of the receiver, in correcting the auto-correlation function of the GNSS navigation signal received from each satellite of the constellation by means of the delay function, in comparing the corrected auto-correlation function with a theoretical auto-correlation function by applying a quadratic criterion corresponding to the confidence indicator.